September 5, 2012 — There is growing evidence regarding the long-term cardiovascular side effects of using Herceptin (trastuzumab), a popular treatment for aggressive breast cancer. Researchers are warning that the risk of heart failure may be higher than previously thought, because clinical trials under-estimate risks faced by the real-world population. The researchers found that women treated with Herceptin were at least four times more likely to have heart failure than women treated with other cancer medications.

The researchers analyzed medical records for about 12,500 women treated for aggressive breast cancer between 1999 – 2007. The women were 60 years old on average, and the researchers tracked their treatment and outcome for 2-7 years. The researchers collected data on the type of cancer treatment. This data was compared to the incidence of cardiovascular problems during cancer treatment.

Before the researchers began their study, they already knew that anti-cancer drugs increase the risk of heart failure. The anthracycline class (which includes Herceptin) was associated with a 1.4-fold increased risk of heart failure — about the same as other cancer drugs. However, Herceptin alone was associated with a four-fold increased risk of heart failure. Patients treated with an anthracycline in addition to Herceptin had a seven-fold increased risk of heart failure.

The researchers said, “The study suggests the long-term risk for heart failure may be higher in women treated in the community than in clinical trials, particularly women who are older and/or have [other diseases besides the cancer].” The researchers were concerned that the clinical trials of Herceptin may under-estimate the cardiovascular risk of this medication, because most clinical studies do not include people over 70 years old, or those who have other diseases. By excluding these populations, results from clinical trials may not accurately represent the actual demographics of people who take the medications.

In conclusion, the authors of the study recommended that physicians should monitor patients for heart problems before and during treatment.

Herceptin (trastuzumab) is a medication used by 25-30% of women with an aggressive type of breast cancer that generates a protein called HER-2. Herceptin was first approved in 1998, and it is sold by the drug company Roche. Currently, Roche is conducting studies to compare the risks and benefits of Herceptin compared to other cancer drugs. Roche is conducting a two-year study, and French researchers are conducting a six-month study.